Various types of seat belt and airbag systems have been used to protect passengers in automobiles, aircraft, and other vehicles. In automobiles, for example, airbags typically deploy from the steering column, dashboard, side panel, and/or other fixed locations. In aircraft, airbags can deploy from seat belts (e.g., lap or shoulder belts), seats and/or other aircraft structures. In a typical airbag system, a sensor detects a rapid deceleration event (e.g., a collision or crash) and transmits a corresponding signal to an initiation device (e.g., a pyrotechnic device) on an airbag inflator. This causes the inflator to release compressed gas into the airbag, thereby rapidly inflating and deploying the airbag.
A typical airbag is designed to deploy toward an occupant and slow the velocity of the occupant to a rate that is non-injurious or reduces injury. Generally, the airbag is positioned between the occupant and the surrounding structure in the direction of impact. As the occupant contacts the airbag, the airbag is compressed against and/or into the surrounding structure and the internal pressure increases. As the internal airbag pressure increases, the rate of occupant deceleration also increases, and can become excessively high. The rate of deceleration can be reduced by using vents in the airbag to release some of the internal pressure during occupant impact. Such vents cannot release all the internal pressure during impact, however, because doing so would greatly reduce occupant protection. After the initial contact, compression of the airbag continues until the occupant's movement is momentarily arrested. At that time, the compressed airbag accelerates the occupant in an opposite direction (e.g., rearward toward the seat in which the occupant was seated). This is known as “airbag rebound.” Improved airbag systems are needed to enhance occupant protection by actively deflating airbags to reduce airbag rebound.